In recent years, in view of energy saving and environmental conservation, light emitting devices (LED flashes) using a light-emitting diode (hereinafter also referred to as “LED”) as a light source have been increasingly used for a light emitting device in an imaging camera. A well-known example of such light emitting devices is a light emitting device using a combination of an LED and a Fresnel lens (see, for example, PTL 1).
FIG. 1A is a sectional view of the light emitting device disclosed in PTL 1. As illustrated in FIG. 1A, light emitting device 10 disclosed in PTL 1 includes substrate 20, light source substrate 21, light source 30 including a light emitting element and a phosphor, and Fresnel lens 40. Fresnel lens 40 is disposed on substrate 20 in such a manner as to face the light emitting surface of light source 30.
FIG. 1B is a sectional view of Fresnel lens 40. As illustrated in FIG. 1B, refractive Fresnel lens section 41 and reflective Fresnel lens section 42 are formed on one side of Fresnel lens 40. Refractive Fresnel lens section 41 is formed at a position which faces light source 30. Reflective Fresnel lens section 42 is formed around refractive Fresnel lens section 41 in such a manner as to surround light source 30. In Fresnel lens 40, the surface on which refractive Fresnel lens section 41 and reflective Fresnel lens section 42 are formed functions as incidence region 43, and the surface on the side opposite to incidence region 43 functions as emission region 44.
In light emitting device 10 illustrated in FIG. 1A, light emitted in a forward direction (upward direction in the drawing) from light source 30 is refracted in a predetermined direction at refractive Fresnel lens section 41, and is then output from emission region 44. On the other hand, light emitted in a lateral direction (horizontal direction in the drawing) from light source 30 is incident on incidence surface 45 of reflective Fresnel lens section 42, and is reflected in a predetermined direction by reflecting surface 46, and is then, output from emission region 44. In this manner, light emitting device 10 disclosed in PTL 1 controls the distribution of the light emitted from light source 30 with use of Fresnel lens 40 including refractive Fresnel lens section 41 and reflective Fresnel lens section 42.